In the art of pneumatic tools for tightening threaded fasteners there have been several inventions concerning mechanisms which are operable upon sensing a predetermined torque transmitted by the tool drive mechanism to actuate a motive fluid shutoff valve through an actuating member interconnecting the torque sensing mechanism and the shutoff valve closure member. Prior art devices such as, for example, disclosed in U.S. Pat. Nos. 3,616,864 and 4,078,618 assigned to the assignee of the present invention, have been adapted for use with tools known in the art as "push-to-start" types wherein an operator applied force on the tool proper opens the shutoff valve when the fastener is engaged by the tool. Accordingly, prior art devices of the general type to which the present invention pertains have not been adaptable to tools which are not of the so-called "push-to-start" type.